Highly-refractive plastic lens

ABSTRACT

A plastic lens formed from a copolymer of three components. A first component which is a vinyl monomer having a nucleus-halogen-substituted aromatic ring. A second component which is selected from at least one member of the group consisting of aliphatic diacrylate, dimethacrylate, triacrylate, and trimethacrylate. A third component is chosen from mono-acrylate or mono-methacrylate having a nucleus-halogen substituted aromatic ring. The components are present in the weight ratio of 20/15/0 to 85/80/60 weight percent, respectively.

This application is a continuation of application Ser. No. 777,147 filedSept. 18, 1985, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a plastic lens for spectacles which has highrefractive index, transparency and heat resistance.

2. Description of Prior Art

A plastic lens is advantageous over a glass lens because it is light,easy to dye, and safe when it is used as a spectacle lens because of itshigh impact resistance.

Various resins such as an acrylic resin, a polycarbonate resin, an allyldiglycolcarbonate resin, a polystyrene resin and the like haveheretofore been used for a plastic lens. Among these, diethylene glycolbisallylcarbonate, which is a thermosetting resin, is widely used for anophthalmic lens because it has several advantages, such as high impactresistance, excellent cutting property and processability.

However, the lens of this resin is thicker at the peripheral edgeportion than that of a glass lens because the refractive index ofdiethylene glycol bisallylcarbonate is about 1.50. This defect is moreprominent as the degree of the lens is increased.

Various resins for plastic lenses free from the abovementioned defecthave recently been proposed. For example, British Pat. No. 2,034,721teaches that a copolymer of a dimethacrylate having a bisphenol groupwith chlorostyrene has a refractive index of 1.591. Japanese PatentPublication No. 14449/83 teaches that a copolymer of a dimethacrylatehaving a tetrabromobisphenol group which chlorostyrene has a refractiveindex of 1.599 to 1.608. Laid-Open Japanese Patent Publication No.12501/85 teaches that a copolymer of a tetrachloro diallylterephthalatewith chlorostyrene has a refractive index of 1.600 to 1.609 andLaid-Open Japanese Patent Publication No. 14202/85 teaches a copolymerof a tetrabromo diallylphthalate with phenoxyethylacrylate has arefractive index of 1.595.

Though these resins have higher refractive index that that of crownglass (nd=1.52), they are inferior in toughness and heat resistance.Further, since the monomer mixture containing the above mentionednucleus-halogensubstituted polyfunctional vinyl monomer used as a highrefractive index component is viscous because of its high molecularweight the casting process is not easy.

For imparting a good toughness, mixing or copolymerizing these resinwith polyurethane has been known. For example, U.S. Pat. No. 4,487,904teaches that a copolymer of a nucleus-halogen substituted vinyl monomer(containing hydroxyl groups) and polyfunctional isocyanate with anothervinyl monomer shows a refractive index of 1.61 to 1.63 together withgood toughness.

However, the refractive index of these copolymers is still lower thanthat of high refractive index glass lenses (nd=1.6 to 1.8). Moreover, inordinary cases, whenever the refractive index is increased, the Abbenumber is decreased (the chromatic aberration is increased), which isdisadvantageous.

OBJECT OF THE INVENTION

It is the object of the present invention to provide a plastic lens,which has a refractive index of at least 1.63, preferably at least 1.63and especially at least 1.65 and which has excellent property in respectof chromatic aberration together with high refractive index, that is,the Abbe number is at least 40 and the refractive index is at least 1.60and which is also excellent in toughness, transparency and heatresistance.

SUMMARY OF THE INVENTION

This invention provides a plastic lens which comprises a copolymer of avinyl monomer having a nucleus-halogen-substituted aromatic ring(component A) with at least one member selected from the groupconsisting of divinylbenzene, diacrylate, dimethacrylate, triacrylateand trimethacrylate (component B).

Typical examples of component A and component B are represented by thefollowing formulae I, II, III, IV, V, VI and I', respectively.

All of the components represented by the formulae I, I', II, III and IVare liquid at room temperature, which is advantageous in a castingoperation. ##STR1##

Preferred is a mixture of 2/3 meta- and 1/3 para-divinylbenzene.##STR2## Wherein each of R₁, R₂ R₃ and R₄ are a methyl group orhydrogen, X is chlorine, bromine or iodine, Y is one ##STR3## whereby

b is an integer of from 3 to 10,

Z is a polyfunctional isocyanate residue, A is ##STR4## or --SO₂ --, lis an integer of from 1 to 10, and m and n are integers of from 0 to 4with the proviso that the sum of m and n is an integer of from 0 to 4, pis an integer of from 1 to 4, and q is an integer of from 2 to 3.

PREFERRED EMBODIMENT OF THE INVENTION

As the above mentioned vinyl monomer having anucleus-halogen-substituted aromatic ring (component A) compoundsrepresented by the following formulae (V) and (VI) are preferably usedin the present invention: ##STR5## (wherein X is chlorine, bromine oriodine, R₅ is hydrogen or a methyl group, W is one of ##STR6## r is aninteger of 1 to 5, and the sum of r and s is an integer of from 1 to 5.

Other vinyl monomers may be used in an amount of up to 60% by weight,preferably up to 50% by based on the total weight of the monomers. Forthe other monomers, monomers having an aromatic ring or a halogen(except fluorine) are preferable because they do not decrease therefraction index.

As specific examples of the compounds of the formula (II) among thecomponent B, that is radical polymerizable polyfunctional monomers,there can be mentioned ethylene glycol dimethacrylate, diethylene glycoldiacrylate, diethylene glycol dimethacrylate, triethylene glycoldiacrylate, triethylene glycol dimethacrylate, tetraethylene glycoldiacrylate, tetraethylene glycol dimethacrylate, propylene glycoldiacrylate, propylene glycol dimethacrylate, dipropylene glycoldiacrylate, dipropylene glycol dimethacrylate, trimethylene glycoldimethacrylate, tetramethylene glycol dimethacrylate, pentamethyleneglycol dimethacrylate, 1,6-hexane glycol diacrylate and 1,6-hexaneglycol dimethacrylate.

Among the foregoing compounds, ethylene glycol dimethacrylate,diethylene glycol diacrylate, diethylene glycol dimethacrylate,triethylene glycol dimethacrylate, 1,6-hexane glycol diacrylate,1,6-hexane glycol dimethacrylate and their mixtures are preferred.

By using the above mentioned compounds with a component A, that is, avinyl monomer having a nucleus-halogen-substituted aromatic ring, theplastic lens is obtained having the following improved characteristic.

(1) A high refractive index with a high Abbe number (the chromaticaberration is low) is attained.

(2) The properties such as toughness, heat resistance and cuttingprocessability are improved.

By using divinyl benzene with a component B, the plastic lens isobtained having the following improved characteristic.

(1) An exceedingly high refractive index is achieved (nd≧1.63).

(2) The properties such as toughness, heat resistance and cuttingprocessability are improved.

As specific examples of the compounds of the formula (III) among thecomponent B, that is, radical polymerizable polyfunctional monomers,there can be mentioned the compounds of the addition reaction of amonohydroxy monoacrylate or a monohydroxy monomethacrylate having abisphenol A or bisphenol S in the molecule (hereinafter referred to asVII), with a polyfunctional isocyanate.

As specific examples of the compounds of the formula VII, there can bementioned2-(4-hydroxyethoxy-3,5-dibromophenyl)-2-(4-acryloxyethoxy-3,5-dibromophenyl)propane,2-(4-hydroxyethoxy-3,5-dibromophenyl)-2-(4-methacryloxyethoxy-3,5-dibromophenyl)propane,2-(4-hydroxyethoxy-3,5-dibromophenyl)-2-(4-acryloxy-3,5-dibromophenyl)propane,2-(4-hydroxyethoxy-3,5-dibromophenyl)-2-(4-methacryloxy-3,5-dibromophenyl)propane,2-(4-hydroxy-3,5-dibromophenyl)-2-(4-acryloxy-3,5-dibromophenyl)propane,2-(4-hydroxy-3,5-dibromophenyl)-2-(4-methacryloxy-3,5-dibromophenyl)propane,2-(4-hydroxydiethoxy-3,5-dibromophenyl)-2-(4-acryloxydiethoxy-3,5-dibromophenyl)propaneand2-(4-hydroxydiethoxy-3,5-dibromophenyl)-2-(4-methacryloxydiethoxy-3,5-dibromophenyl)propane,4-hydroxyethoxy-3,5-dibromophenyl-4'-acryloxyethoxy-3',5'-dibromophenylsulfone,4-hydroxyethoxy-3,5-dibromophenyl-4'-methacryloxyethoxy-3',5'-dibromophenylsulfone,4-hydroxyethoxy-3,5-dibromophenyl-4'-acryloxy-3',5'-dibromophenylsulfone,4-hydroxyethoxy-3,5-dibromophenyl-4'-methacryloxy-3',5'-dibromophenylsulfone, 4-hydroxy-3,5-dibromophenyl-4'-acryloxy-3',5'-dibromophenylsulfone, 4-hydroxy-3,5-dibromophenyl-4'-methacryloxy-3',5'-dibromophenylsulfone, 4-hydroxydiethoxy-3,5-dibromophenyl-4'-acryloxydiethoxy-3',5'-dibromophenylsulfone, and4-hydroxydiethoxy-3,5-dibromophenyl-4'-methacryloxydiethoxy-3',5'-dibromophenylsulfone.

Among the foregoing compounds,2-(4-hydroxyethoxy-3,5-dibromophenyl)-2-(4-acryloxyethoxy-3,5-dibromophenyl)propane,2-(4-hydroxyethoxy-3,5-dibromophenyl)-2-(4-methacryloxyethoxy-3,5-dibromophenyl)propaneand mixtures thereof are preferred.

The above-mentioned compounds may be used alone or in the form of amixture of two or more of them.

As the polyfunctional isocyanate, there can be mentioned diisocyanatessuch as hexamethylene diisocyanate, isophorone diisocyanate,2,2,4-trimethyl-hexamethylene diisocyanate, dicyclohexylmethanediisocyanate, lysine diisocyanate methyl ester, xylylene diisocyanate,bis(isocyanatomethyl)cyclohexane, tolylene diisocyanate and4,4'-diphenylmethane diisocyanate, and polyfunctional isocyanates havinga functionality of 3 such as a biuret reaction product of hexamethylenediisocyanate, an adduct of hexamethylene diisocyanate totrimethylolpropane, 2-isocyanatoethyl-2,6-diisocyanatohexanoate,1,6,11-undecane triisocyanate, an adduct of isophorone diisocyanate withtrimethylolpropane, an adduct of xylylene diisocyanate withtrimethylolpropane and an adduct of bis(isocyanatomethyl)cyclohexanewith trimethylolpropane.

Among the foregoing compounds, hexamethylene diisocyanate, xylylenediisocyanate, 2-isocyanatoethyl-2,6-diisocyanatehexanoate,1,6,11-undecane triisocyanate are preferred.

The molar ratio between the acrylic or methacrylic monomer (VII) and thepolyfunctional isocyanate is such that the NCO/OH molar ratio is in therange of from 0.5 to 2.0, preferably from 0.8 to 1.0. If the NCO/OHmolar ratio is lower than 0.5, the impact strength is reduced, andfurthermore, the flexural strength, heat softening property and cuttingor grinding property are degraded. If the NCO/OH molar ratio exceeds2.0, the polymer is readily discolored.

When the acrylic or methacrylic monomer (VII) is reacted with thepolyfunctional isocyanate, the hydroxyl group of the acrylic ormethacrylic monomer (VII) reacts with the isocyanate group of thepolyfunctional isocyanate to form a urethanized acrylic or methacrylicmonomer (III).

By using the urethanized acrylic or methacrylic monomer III with acomponent A, that is a vinyl monomer having anucleus-halogen-substituted aromatic ring, the plastic lens is obtainedhaving the following improved characteristic.

(1) An exceedingly high refractive index is achieved.

(2) The impact strength is improved.

(3) The properties such as toughness, heat resistance and cuttingprocessability are improved.

The preferred halogen substituent in the compounds of formulae III, IV,V and VI is bromine.

As specific examples of the compounds of the formula IV among thecomponent B, that is, radical polymerizable polyfunctional monomers,there can be mentioned the compounds of the addition reaction of aphenoxymonoacrylate or phenoxymonomethacrylate having a hydroxyl groupin the molecule (hereinafter referred to as VIII), with polyfunctionalisocyanate.

As specific examples of the compounds of the formula VIII, there can bementioned 3-(2,4-dibromophenoxy)-2-hydroxypropyl acrylate,3-(2,4,6-tribromophenoxy)-2-hydroxypropyl acrylate,3-(2,4-dibromophenoxy)-2-hydroxypropyl methacrylate,3-(2,4,6-tribromophenyoxy)-2-hydroxypropyl methacrylate,3-(2,4-iodophenoxy)-2-hydroxypropyl acrylate,3-(2,4,6-triiodophenoxy)-2-hydroxypropyl acrylate,3-(2,4,6-tribromo-3-methylphenoxy)-2-hydroxypropyl acrylate,3-(2,4-dibromo-3-methylphenoxy)-2-hydroxypropyl acrylate,3-(2,6-diiodo-3-methylphenoxy)-2-hydroxypropyl acrylate,3-(2,4,6-tribromo-3-methylphenoxy)-2-hydroxypropyl methacrylate,3-(3-methyl-5-bromophenoxy)-2-hydroxypropyl acrylate and3-(3-methyl-5-iodophenoxy)-2-hydroxypropyl methacrylate. Among theforegoing compounds, 3-(2,4,6-tribromophenyoxy)-2-hydroxypropylacrylate, 3-(2,4-dibromophenoxy)-2-hydroxypropyl acrylate and3-(2,4-iodophenoxy)-2-hydroxypropyl acrylate compounds,3-(2,4,6-tribromo-3-methylphenoxy)-2-hydroxypropyl acrylate,3-(2,4-dibromo-3-methylphenoxy)-2-hydroxypropyl acrylate,3-(3-methyl-5-bromophenoxy)-2-hydroxypropyl acrylate and mixturesthereof are preferred. The above-mentioned compounds may be used aloneor in the form of a mixture of two or more of them.

The species of the polyfunctional isocyanates and the molar ratiobetween the acrylic or methacrylic monomer VIII and the polyfunctionalisocyanates may be used as same as the case of the acrylic ormethacrylic monomer VII.

By using the urethanized acrylic or methacrylic monomer IV with acomponent A, that is a vinyl monomer having anucleus-halogen-substituted aromatic ring, a plastic lens is obtainedhaving the following improved characteristic.

(1) An exceedingly high refractive index is achieved.

(2) The impact strength is improved.

(3) The properties such as toughness, heat resistance and cuttingprocessability are improved.

As specific examples of the compounds of the formula V among thecomponent A, that is, vinyl monomers having anucleus-halogen-substituted aromatic ring, there can be mentioneddibromostyrene, bromostyrene, dichlorostyrene, chlorostyrene,diiodostyrene, iodostyrene, methylbromostyrene methylchlorostyrene andso forth, and their mixtures.

Particularly preferable thereamong are bromostyrenes especiallydibromostyrene.

As specific examples of the compounds of the formula VI among thecomponent A, that is, vinyl monomers having anucleus-halogen-substituted aromatic ring, there can be mentioned3-(2,3,4,5,6-pentabromophenoxy)-2-hydroxypropyl acrylate,2,3,4,5,6-pentabromophenoxyethyl acrylate,2,3,4,5,6-pentabromophenoxyethyl methacrylate,3-(2,4,6-tribromophenoxy)-2-hydroxypropyl acrylate,3-(2,4,6-tribromophenoxy)-2-hydroxypropyl methacrylate,2,4,6-tribromophenoxypropyl acrylate, 2,4,6-tribromophenoxypropylmethacrylate, 3-(2,4,6-tribromo-3-methylphenoxy)-2-hydroxypropylacrylate, 2-(2,4,6-tribromo-3-methylphenoxy)-1-hydroxymethylethylacrylate, 2,4-dibromophenoxyethyl acrylate,3-(2,4-dibromophenoxy)-2-hydroxypropyl acrylate,3-(2,4-dibromo-3-methylphenoxy)-2-hydroxypropyl acrylate,3-(2,3,4,5,6-pentachlorophenoxy)-2-hydroxypropyl acrylate,2,4,6-trichlorophenoxyethyl methacrylate, 2,4,6-tribromophenoxyethylacrylate, 2,4,6-tribromophenoxyethyl methacrylate, and so forth.

Particularly preferable among the above compounds are3-(2,3,4,5,6-pentabromophenoxy)-2-hydroxypropyl acrylate,2,4,6-triblomophenoxyethyl methacrylate, 2,4,6-tribromophenoxyethylacrylate, 2,3,4,5,6-pentabromophenoxyethyl acrylate,2,3,4,5,6-pentabromophenoxyethyl methacrylate and their mixtures.

The copolymerization ratio of the vinyl monomer having anucleus-halogen-substituted aromatic ring (A) to theradical-polymerizable polyfunctional monomer (B) should be at 10 to 90,preferably 20-85, percent by weight based on the sum of the monomers (A)and (B). If the copolymerization ratio of the vinyl monomer (A) exceeds90 percent by weight, not only the cutting or grinding property but alsothe impact strength, and the heat resistance are degraded because of theshortage of crosslinkage among the monomers. While if thecopolymerization ratio of the vinyl monomer (A) is below 10 percent byweight, the intended improvement of the high refractive index cannot beattained.

In order to improve or control other properties for an ophthalmic lens,the above mentioned monomers A and B are copolymerized with anothervinyl monomer(s) having an aromatic ring and/or halogen (exceptfluorine) in the molecule. This other vinyl monomer having an aromaticring and/or halogen (except fluorine) in the molecule may be used in anamount of up to 70 percent, preferably up to 60 percent by weight basedon the total weight of the monomers.

As specific examples of the other vinyl monomer having an aromatic ringand/or halogen (except fluorine), there can be mentioned styrene, phenylacrylate, phenyl methacrylate, monochlorophenyl acrylate,monochlorophenyl methacrylate, dichlorophenyl acrylate, dichlorophenylmethacrylate, trichlorophenyl acrylate, trichlorophenyl methacrylate,monobromophenyl acrylate, monobromophenyl methacrylate, dibromophenylacrylate, dibromopnenyl methacrylate, tribromophenyl acrylate,tribromophenyl methacrylate, pentabromophenyl acrylate, pentabromophenylmethacrylate, 2,2-bis(4-methacryloxyethoxy-3,5-dibromophenyl)propane,2,2-bis(4-acryloxyethoxy-3,5-dibromophenyl)propane, diallyl phthalate,diallyl isophthalate, N-vinylcarbazole, benzyl acrylate, bromobenzylacrylate, dibromobenzyl acrylate, vinylnaphthalene, naphthylmethacrylate, triallyl, trimellitate, 2,3-dibromopropyl acrylate,tribromoneopentyl acrylate, tribromoneopentyl methacrylate,2,2-bis(4-methacryloxy-3,5-dibromophenyl)sulfone,2,2-bis(4-acryloxy-3,5-dibromophenyl)sulfone,2,2-bis(4-methacryloxyethoxy-3,5-dibromophenyl)sulfone,2,2-bis(4-acryloxyethoxy-3,5-dibromophenyl)sulfone and their mixtures.

Among the foregoing compounds, tribromoneopentyl acrylate,tribromoneopentyl methacrylate, tribromoneopentyl methacrylate,2,2-bis(4-methacryloxyethoxy-3,5-dibromophenyl)propane,2,2-bis(4-acryloxyethoxy-3,5-dibromophenyl)propane,2,2-bis(4-methacryloxyehoxy-3,5-dibromophenyl)sulfone,2,2-bis(4-acryloxyethoxy-3,5-dibromophenyl)sulfone and their mixturesare preferred.

If the other vinyl monomer above-mentioned exceeds 70 percent by weight,the toughness the impact strength, the heat resistance and the cuttingor grinding property are decreased.

The plastic lens according to the subject invention is extensivelyapplicable as a spectacle, convex or concave, for optical apparatuses,and so forth. Particularly its thickness and weight can be decreasedbecause of its high refractive index. It is especially useful as theconcave lens of the spectacles for the short-sighted in which thickportion at the peripheral edge portion spoils the appearance.

In this invention, a cast polymerization is adopted in which thestarting monomers are directly polymerized and cured and simultaneouslymolded into the form of a lens.

Most of commercially available dioptral lenses are now prepared by thismethod because the molding distortion is reduced and the obtained lensis excellent in optical uniformity.

The monomers (A), (B) and/or other vinyl monomers are mixed together,and a polymerization initiator is added to the mixture to preliminarilypolymerize to some extent (prepolymerization). After dissolved gasessuch as air are removed in vacuo, the pre-polymerization product is castin a mold, where polymerization is carried out under heating.

In order to reduce the distortion in the resulting lens, it is preferredthat in the initial stage, the polymerization reaction by carried out ata relatively low temperature, for example, 40° to 50° C. and thetemperature be elevated to about 110° C. to 130° C. to gradually effectpolymerization.

Any of known polymerization initiators can be used, but an appropriatepolymerization initiator should be selected depending upon the intendedreaction temperature. For example, there are preferably useddiisopropylperoxy dicarbonate, t-butylperoxyethyl hexanoate,t-butylperoxy isobutylate, t-butylperoxyisopropyl carbonate, di-t-butylperoxide, 1,1-azobiscyclohexane carbonate, 1,1'-azobiscyclohexanenitrate, azobisisobutyronitrile and so forth.

Depending on polymerization conditions and the kind of the monomers ofcopolymerization components, the kind and ratio of the radicalpolymerization initiators cannot be limited. However, the latter shouldpreferably be 0.001 to 5 percent by weight to the total quantity ofmonomers.

An appropriate additive selected from a surface lubricant, anultraviolet absorber, an antioxidant, a discoloration-preventing agent,an antistatic agent, a fluorescent dye and a stabilizer may be used atthe polymerization step according to need.

The plastic lens of this present invention has the following improvedcharacteristic as compared with commercially available plastic lenses.

(1) An exceedingly high refractive index is achieved.

(2) The properties such as toughness, transparence, heat resistance andcutting or grinding processability are improved.

(3) The monomers (A), (B) and/or other vinyl monomers can appropriatelybe chosen, whereby the optical characteristics can be freely adjusted.

The plastic lens of this present invention may be subjected to a knownphysical of chemical surface treatment for imparting thereflection-preventing property, high hardness, abrasion resistance,chemical resistance and anti-fogging property. For example, there ispreferably adopted a method in which two coatings of differentrefractive indexes are formed to attain a reflection-preventing effect,a method in which a coating layer having a high hardness is formed onthe surface by coating with a polysiloxane or silica sol, a method inwhich a surface coating is dyed to improve the fashion characteristic, amethod in which a metal film is formed on the surface by vacuumdeposition or the like to impart a mirror effect, and a method in whicha moisture-adsorbing coating is formed on the surface to preventfogging.

Further the structure and components of the lens of this invention canbe analyzed by means of IR, NMR, elementary analysis and so forth.

This invention is described in detail with reference to the followingexamples and comparative examples. From the results of these examplesand comparative examples, it would be easily understood that the plasticlens of this invention is superior both in optical characteristics andthe other properties as ophthalmic lens. Of course, these examples by nomeans limit the scope of the invention.

In the examples and comparative examples, the physical properties weredetermined according to the following methods.

Refractive Index and Abbe Number:

The measurement was carried out at 20° C. by using an Abberefractometer.

n_(d) was measured at d-line of He (587.6 nm) and ν_(d) was calculatedby following equation. ##EQU1##

n_(F) ; Refractive index at F-line of H (486.1 nm)

n_(c) ; Refractive index at c-line of H (656.3 nm)

Color:

The color of a plate or molded lens was observed with the naked eye.

Edging processability:

After the grinding a peripheral edge portion of a lens by using anautomatic lens edger (Takubo Machine Works Co., Ltd.), lenses having nocracking, having smooth cutting surface and having produced powderycutting chips were accepted. (This edger is usually used for CR-39 orglass lens).

Vicat Softening test:

VICAT penetration distance at 100° C. was given in the test according toJIS K-7206 because no testpiece reached the maximum penetration of 1 mm.

Rigidity:

Flexural modulas and deflection was determined according to the methodof ASTM D747. Test pieces had a size of 30 mm×10 mm×3 mm.

Flexural deflection means the maximum deflection of the center of thetest piece.

EXAMPLE 1

An amount of 85 parts by weight of dibromostyrene and 15 parts by weightof divinylbenzene (made by Sankyo Kasei Kogyo Co., which purity is 60percent) were mixed and 0.1 part by weight of diisopropylperoxydicarbonate and 0.1 part by weight of di-tert-butyl peroxide were addedas radical-polymerization initiators. The mixture was a colorlesstransparent liquid having a low viscosity.

The liquid mixture was cast in a mold constructed by a glass mold and apolyethylene gasket. The cast polymerization was started from 40° C. andthe temperature was raised stepwise up to 120° C. Thus thepolymerization was conducted over a period of 30 hours.

The polymer obtained was colorless and transparent, and showed anexceedingly high refractive index n_(D) of 1.66 among plastic lenses andan Abbe number of 30.

The other physical properties of the polymer are shown in Table 1.

EXAMPLE 2

An amount of 85 parts by weight of 2,3,4,5,6-pentabromophenoxyethylacrylate and 15 parts by weight of divinylbenzene (made by Sankyo KaseiKogyo Co., 60 percent purity) were mixed and 0.1 part by weight ofdi-tertbutyl peroxide was added. The mixture was sufficiently stirred.This mixture was a colorless, transparent and slightly viscous liquid.

Then the liquid mixture was subjected to vacuum degassing, and was castin a mold constructed from a glass mold having a diameter of 75 mm and apolyethylene gasket. The cast polymerization was continued for 40 hourswith its temperature gradually raised from 60° C. to 130° C. instepwise.

The molding obtained was colorless and transparent and showed arefractive index n_(d) of 1.65 and an Abbe number of 28.

The other physical properties of the polymer are shown in Table 1.

EXAMPLE 3

Lens was made in the same manner as described in Example 2 but using 80parts by weight of 3-(2,3,4,5,6-pentabromophenoxy)-2-hydroxypropylmethacrylate in stead of 85 parts by weight of2,3,4,5,6-pentabromophenoxyethyl acrylate, and using 20 parts by weightof divinylbenzene (made by Dow Chemical Co., 80 percent purity) insteadof 15 parts by weight of divinylbenzene (made by Sankyo Kasei Kogyo Co.,60 percent purity). The polymer obtained was colorless and transparent,and showed a refractive index n_(D) of 1.65 and an Abbe number of 29.The other physical properties of the polymer are shown in Table 1.

EXAMPLE 4

To a mixture of 40 parts by weight of dibromostyrene, 40 parts by weightof 2,3,4,5,6-pentabromophenoxyethyl acrylate and 20 parts by weight ofdivinylbenzene (made by Dow Chemical Co., 80 percent purity) was added0.1 part by weight of di-tert-butyl peroxide, and the mixture wassufficiently stirred. The mixture was a colorless, transparent and lowviscous liquid. The cast polymerization was carried out in the samemanner as described in Example 2.

The polymer obtained was colorless and transparent, and showed arefractive index n_(D) of 1.65 and an Abbe number of 30.

The other physical properties of the polymer are shown in Table 1.

EXAMPLE 5

0.01 part by weight of dibutyltin dilaurate as an NCO-OH reactioncatalyst and 0.1 part by weight of di-tert-butyl peroxide as apolymerization initiator were added to 3.6 parts by weight of xylylenediisocyanate, 26.4 parts by weight of2-(4-acryloxyethoxy-3,5-dibromophenyl)-2-(4-hydroxyethoxy-3,5-dibromophenyl)propaneand 70 parts by weight of dibromostyrene and the mixture wassufficiently stirred. The obtained liquid mixture had a low viscosityand could easily be cast in a lens mold. The cast polymerization wascarried out in the following manner using a glass mold and apolyethylene gasket.

Namely, the mixture was heated at 60° C. for 5 hours to complete theNCO/OH reaction, and subsequently, the resulting liquid mixture washeated at 80° C. for 5 hours, at 90° C. for 5 hours, at 100° C. for 9hours, at 110° C. for 9 hours and at 120° C. for 5 hours to effectcuring reaction.

After completion of the polymerization, the mold was gradually cooledand the polymer was parted from the mold.

The polymer obtained was colorless, transparent, and tough, and showed arefractive index n_(D) of 1.65 and an Abbe number of 31.

The other physical properties of the polymer are shown in Table 1.

EXAMPLE 6

An amount of 2.4 parts by weight of xylylene diisocyanate, 17.6 parts byweight of2-(4-acryloxyethoxy-3,5-dibromophenyl)-2-(4-hydroxyethoxy-3,5-dibromophenyl)propane,70 parts by weight of dibromostyrene and 10 parts by weight ofdivinylbenzene (made by Dow Chemical Co., 80 percent purity) were mixedand 0.01 part by weight of dibutyltin dilaurate as an NCO-OH reactioncatalyst and 0.1 part by weight of tert-butyl peroxy isopropyl carbonatewere added and the mixture was sufficiently stirred. The NCO-OH reactionand the polymerization reaction in a glass mold and a polyethylenegasket were carried out in the same manner as described in Example 5.The polymer obtained was colorless, transparent and tough, and showed arefractive index n_(D) of 1.65 and an Abbe number of 31.

The physical properties of the polymer are shown in Table 1.

EXAMPLE 7

A mixture comprising 1.1 parts by weight of hexamethylene diisocyanate,8.9 parts by weight of2-(4-acryloxyethoxy-3,5-dibromophenyl)-2-(4-hydroxyethoxy-3.5-dibromophenyl)propane,45 parts by weight of dibromostyrene, 18 parts by weight of2,3,4,5,6-pentabromophenoxyethyl methacrylate, 27 parts by weight of2,2-bis(4-acryloxyethoxy-3,5-dibromophenyl)sulfone and 0.01 part byweight of dibutyltin dilaurate was stirred and heated at 50° C. for 2hours to conduct the reaction. The reaction mixture was cooled to roomtemperature and 0.1 part by weight of tert-butyl peroxy isopropylcarbonate as a polymerization initiator was added. The resulting mixturewas a slightly viscous liquid and could easily be cast in a lens mold.The polymerization reaction was carried out in the same manner asdescribed in Example 5. The obtained resin was tough, colorless andtransparent and was excellent in uniformity. The refractive index n_(D)as measured at 20° C. was as high as 1.65 and the Abbe number was 31.

Other physical properties of the polymer are shown in Table 1.

EXAMPLE 8

An amount of 60 parts by weight of dibromostyrene, 10 parts by weight of2,3,4,5,6-pentabromophenoxyethyl acrylate and 30 parts by weight of1,6-hexane dimethacrylate were mixed and 0.01 part by weight oftert-butyl peroxy isobutylate and 0.04 part by weight of tert-butylperoxy isopropyl carbonate were added. The mixture was sufficientlystirred. The obtained mixture was a colorless transparent liquid havinga low viscosity. After being subjected to the vacuum degassing, thisliquid mixture was cast in a lens mold. The polymerization was startedat 60° C. and the temperature was elevated stepwise from 60° C. to 110°C. for 40 hours. The obtained polymer was tough, colorless andtransparent, and the refractive index n_(D) was as high as 1.60 and theAbbe number was which was excellent in chromatic aberration.

Other physical properties of the polymer are shown in Table 1.

EXAMPLE 9

An amount of 45 parts by weight of dibromostyrene, 20 parts by weight of2,3,4,5,6-pentabromophenoxyethyl acrylate and 35 parts by weight ofethylene glycol dimethacrylate were mixed and 0.01 part by weight oftert-butyl peroxy isobutylate and 0.04 part by weight of tert-butylperoxy isopropyl carbonate were added. The mixture was sufficientlystirred. The obtained mixture was a colorless transparent liquid havinga low viscosity. The cast polymerization was carried out in the samemanner as described in Example 8.

The molding obtained was colorless, transparent and rigid, and showed ahigh refractive index n_(D) of 1.60 and an Abbe number of 40, which wasexcellent in chromatic aberration.

The other physical properties of the molding are shown in Table 1.

EXAMPLE 10

A lens was made in the same manner as described in Example 8 but using40 parts by weight of dibromostyrene, 20 parts by weight ofdivinylbenzene (made by Dow Chemical Co., 80 percent purity) and 40parts by weight of tribromopentyl acrylate instead of monomers and theirquantities used in Example 8. The polymer obtained was colorless andtransparent, and showed a refractive index n_(D) of 1.60 and an Abbenumber of 40, which was excellent in a chromatic aberration.

Other physical properties of the polymer are shown in Table 1.

COMPARATIVE EXAMPLE 1

An amount of 40 parts by weight of styrene and,2,2-bis(4-methacryloxyethoxy-3,5-dibromophenyl)propane were mixed, and0.1 part by weight of di-tert-butyl peroxide and 0.1 part by weight ofdiisopropylperoxy dicarbonate were added as radical-polymerizationinitiators. The polymerization was carried out in the same manner asdescribed in Example 1.

The polymer obtained was colorless and transparent, but was not good intoughness and heat resistance. The refractive index n_(D) was 1.59 andthe Abbe number was 32.

COMPARATIVE EXAMPLE 2

0.01 part by weight of dibutyltin dilaurate as an NCO-OH reactioncatalyst and 0.1 part by weight of di-tert-butyl peroxide as apolymerization initiator were added to 40 parts by weight of styrene, 6parts by weight of hexamethylene diisocyanate and 54 parts by weight of2-(4-acryloxyethoxy-3,5-dibromophenyl)-2-(hydroxyethoxy-3,5-dibromophenyl)propaneand the mixture was sufficiently stirred.

The polymerization was carried out in the same manner as described inExample 5.

The polymer obtained was colorless and transparent, but not sufficientin heat resistance. The refractive index n_(D) was 1.60 and the Abbenumber was 32.

Other physical properties of the polymer are shown in Table 1.

COMPARATIVE EXAMPLE 3

An amount of 70 parts by weight of 2,3-dibromopropyl methacrylate; and30 parts by weight of2,2-bis(4-methacryloxyethoxy-3,5-dibromophenyl)sulfone were mixed, and0.1 part by weight of di-tert-butyl peroxide were added.

The polymerization was carried out in the same manner as described inExamples 1. The polymer obtained was colorless and transparent, but wasnot sufficient in heat resistance and toughness either.

The refractive index n_(D) was 1.59 and the Abbe number was 38.

Other physical properties of the polymer are shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________                                                              Cut-                                                                          ting                                                                   Flex-                                                                             Flex-                                                                            and                                                Re-                 ural                                                                              ural                                                                             Crind-                                             frac-                                                                            Abbe      VICAT  Modu-                                                                             De-                                                                              ing                                                tive                                                                             num-      penetra-                                                                             las flec-                                                                            Prop-                     Monomer composition      index                                                                            ber       tion   (kg/                                                                              tion                                                                             er-                 No.   (wt %)                   n.sub.d                                                                          ν.sub.D                                                                        Color (mm/100° C.)                                                                  mm) (mm)                                                                             ties                __________________________________________________________________________    Example 1                                                                           Br.sub.2 ST/DVB (85/15)  1.66                                                                             30  Colorless,                                                                          <0.05  290 0.6                                                                              Good                                                      transparent                             Example 2                                                                           PBPEA/DVB (85/15)        1.65                                                                             28  Colorless,                                                                          0.02   310 1.0                                                                              Good                                                      transparent                             Example 3                                                                           PBPHM/DVB (80/20)        1.64                                                                             29  Colorless,                                                                          0.02   300 0.7                                                                              Good                                                      transparent                             Example 4                                                                           Br.sub.2 ST/PBPEA/DVB (40/40/20)                                                                       1.65                                                                             30  Colorless,                                                                          <0.01  310 0.9                                                                              Good                                                      transparent                             Example 5                                                                           Br.sub.2 ST/XDI--AEBr.sub.2 HEBr.sub.2 PP (70/3.6-26.4)                                                1.65                                                                             31  Colorless,                                                                          0.04   410 0.6                                                                              Good                                                      transparent                             Example 6                                                                           Br.sub.2 ST/XDI-- AEBr HEBr PP/DVB                                                                     1.65                                                                             31  Colorless,                                                                          0.05   370 0.8                                                                              Good                      (70/2.4-17.6/10)                transparent                             Example 7                                                                           Br.sub.2 ST/PBPEA/HMDI--AEBr.sub.2 HEBr.sub.2 PP/BAEBr.sub.2                                           1.65                                                                             31  Colorless,                                                                          0.05   400 0.6                                                                              Good                      (45/18/1.1-8.9/27)              transparent                             Example 8                                                                           Br.sub.2 ST/PBPEA/HDMA (60/10/30)                                                                      1.60                                                                             40  Colorless,                                                                          0.03   300 1.1                                                                              Good                                                      transparent                             Example 9                                                                           Br.sub.2 ST/PBPEA/EGDMA (45/20/35)                                                                     1.60                                                                             40  Colorless,                                                                          <0.05  410 1.0                                                                              Good                                                      transparent                             Example 10                                                                          Br.sub.2 ST/DVB/TBPeA (40/20/40)                                                                       1.61                                                                             40  Colorless,                                                                          0.01   310 0.9                                                                              Good                                                      transparent                             Comparative                                                                         ST/BMEBr.sub.2 PP (40/60)                                                                              1.59                                                                             32  Colorless,                                                                          >0.10  250 2.3                                                                              Good                Example 1                             transparent                             Comparative                                                                         ST/HMDl--AEBr.sub.2 HEBr.sub.2 PP                                                                      1.60                                                                             32  Colorless,                                                                          >0.10  350 1.8                                                                              Good                Example 2                                                                           (40/6-54)                       transparent                             Comparative                                                                         DBPMA/BMEBr.sub.2 PS (70/30)                                                                           1.59                                                                             38  Colorless,                                                                          >0.25  <100                                                                              >2.0                                                                             Poor                Example 3                             transparent                             __________________________________________________________________________

The abbreviations in Table 1 indicate the following compounds.

    ______________________________________                                        Br.sub.2 --ST:                                                                           Dibromostyrene                                                     DVB:       divinylbenzene                                                     PBPEA:     2,3,4,5,6-pentabromophenoxyethyl acrylate                          PBPHM:     3-(2,3,4,5,6-pentabromophenoxy)-2-hydroxy-                                    propyl methacrylate                                                XDI:       xylylene diisocyanate                                              AEBr.sub.2 HEBr.sub.2 PP:                                                                2-(4-acryloxyethoxy-3,5-dibromophenyl)-2-                                     (4-hydroxyethoxy-3,5-dibromophenyl)propane                         BAEBr.sub.2 PS:                                                                          2,2-bis(4-acryloxyethoxy-3,5-dibromophenyl)                                   sulfone                                                            HMDI:      hexamethylene diisocyanate                                         HDMA:      1,6-hexane dimethacrylate                                          EGDMA:     ethylene glycol dimethacrylate                                     TBPeA:     tribromoneopentyl acrylate                                         ST:        styrene                                                            DBPMA:     2,3-dibromopropyl methacrylate                                     BMEBr.sub.2 PP:                                                                          2,2-bis(4-methacryloxyethoxy-3,5-                                             dibromophenyl)propane                                              BMEBr.sub.2 PS:                                                                          2,2-bis(4-methacryloxyethoxy-                                                 3,5-dibromophenyl) sulfone                                         ______________________________________                                    

We claim:
 1. A plastic lens which comprises a copolymer of (A) 20 to 85percent by weight of dibromostyrene with (B) 15 to 80 percent by weightof at least one member selected from the group consisting of aliphaticdiacrylate, dimethacrylate, triacrylate and trimethacrylate, and (C)less than 60 percent by weight of mono-acrylate, or monomethacrylatehaving a nucleus-halogen substituted aromatic ring, said copolymer beingin the form of a lens.
 2. A plastic lens according to claim 1, whereinthe component C is at least one member selected from the grouprepresented by the following general formulae V and VI ##STR7## whereinX is chlorine, bromine or iodine, R₅ is a methyl group or hydrogen, W isone of ##STR8## and r is an integer of from 1 to
 5. 3. A plastic lensaccording to claim 1, wherein the polymer is formed bycast-polymerization.
 4. A plastic lens according to claim 1, whereincomponent B is ethylene glycol dimethacrylate.
 5. A plastic lensaccording to claim 1, wherein component B is aliphatic diacrylate and/ordimethacrylate represented by the following general formulae II.##STR9## wherein R₁ is a methyl group hydrogen, Y is one being selectedout of groups ##STR10## whereby b is an integer of from 3 to 10, l is aninteger of from 1 to
 10. 6. A plastic lens according to claim 1, whereincomponent C is a monomer represented by the following general formulaeVI ##STR11## wherein X is chlorine, bromine, or iodine, R₅ is a methylgroup or hydrogen, W is one being selected out of groups ##STR12## and ris an integer of from 1 to 5, and S in an integer of from 1 to
 4. 7. Aplastic lens according to claim 1, wherein component B is ethyleneglycol dimethacrylate.
 8. A plastic lens according to claim 1, whereincomponent C is 2,3,4,5,6-pentabromophenoxyethyl acrylate.